[1][2] Aguilera co-wrote the song with Johnny Simpson, Mark Williams, Audra Mae, Raul Cubina and Jon Bellion, while the production was handled by the latter.

[3] The song received widespread acclaim from music critics, who commended Aguilera's and Lovato's vocals, as well as the lyrics and inspiring theme.

"[5] In November 2018, the track's songwriter and producer Jon Bellion revealed that at one point, Beyoncé had tried to secure the song for the R&B duo Chloe x Halle.

[9] Aguilera stated in a tweet: "To anyone who's ever felt silenced and repressed, the truth seekers and bold thinkers...may you liberate your voice and break the mold, never back down, and never fall in line.

The track was recorded at The Guest House in Hollywood Hills, California, while the mixing was handled by Manny Marroquin at Larrabee Sound Studios.

[12] "Fall in Line" has been described as a "feminist anthem" and a sequel to Aguilera's 2003 song, "Can't Hold Us Down" with a lyrical content of women's rights.

"[16] Jon Pareles from The New York Times felt that "Fall in Line" is "addressed directly to 'little girls'", pointing out the lyric "You do not owe them your body and your soul",[17] while Brittany Spanos from Rolling Stone described the track as an "empowering duet".

[18] During a review for Liberation for USA Today, Patrick Ryan said that the song is a "soulful riff-off", and Aguilera and Lovato are "belting to the rafters as they preach to young girls the importance of speaking their minds and being themselves".

[19] Chuck Arnold from New York Post described the song as "torchy" and "fiery", also stating that "Fall in Line" is "defiant duo".

[20] Ilana Kaplan and Joe Goggins from The Independent felt that "Fall in Line" is a standout on Liberation, describing it as a "impassioned feminist anthem", and also stating that Aguilera and Lovato are "two of the best vocal powerhouses in the game".

[21] Daniel Kreps of Rolling Stone called Aguilera and Lovato's singing abilities "remarkable" and deemed the final chorus a "skyscraping duet".

[28] Billboard's Danielle Pascual ranked the song at number one on the list of the best Demi Lovato collaborations, praising it for "poignant lyrics" and "powerhouse" vocals.

[38] It depicts Aguilera and Lovato being kidnapped and forced to sing in a futuristic prison filled with surveillance cameras; the two eventually fight their way to freedom.